Aircraft gas turbine engines typically comprise thrust reversers configured to provide a thrust component having a reverse flow direction compared to normal flow in forward flight, or to at least provide additional drag, in order to reduce the speed of the aircraft. One known arrangement comprises a “cold stream” thrust reverser, in which blocker doors are deployed to prevent normal flow through the bypass duct rearwardly of the fan, while permitting flow through the engine core. Simultaneously, a sleeve around the perimeter of the nacelle moves axially rearwards, revealing vanes, which redirect bypass air forward, thereby providing reverse thrust. The vanes are typically configured in discrete cascade boxes, with each cascade box typically having an individual arrangement of forward turning vanes.
However, such arrangements require the provision of vanes over a significant length of the nacelle. The vanes have a relatively large radial thickness, which may increase the overall thickness of the nacelle, and so increase aerodynamic drag in normal flight. Consequently, there is a need to provide an aircraft gas turbine engine nacelle which overcomes or ameliorates the above problems.
Furthermore, in conventional arrangements, the thrust reverser cascade boxes are attached individually to the nacelle thrust reverser unit, with the cascade boxes typically located by attaching bolts along the forward edge of a cascade box to the nacelle frame, and at the rear edge of the cascade box to a large structural aft cascade ring. With this arrangement, the aft support ring for the cascade array forms a key hardpoint defining the nacelle aero surface which can lead to an increased length and diameter nacelle.